Multiwavelength and polarization lidar measurements of

Asian dust layers over Tsukuba, Japan: a case study

T. Sakai, T. Nagai, T. Kobayashi, A. Yamazaki, A. Uchiyama, Y. Mano

To cite this version:

T. Sakai, T. Nagai, T. Kobayashi, A. Yamazaki, A. Uchiyama, et al.. Multiwavelength andpolarization lidar measurements of Asian dust layers over Tsukuba, Japan: a case study. Atmo-spheric Chemistry and Physics Discussions, European Geosciences Union, 2007, 7 (4), pp.10179-10203. <hal-00302967>

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Atmos. Chem. Phys. Discuss., 7, 10179–10203, 2007

www.atmos-chem-phys-discuss.net/7/10179/2007/

© Author(s) 2007. This work is licensed

under a Creative Commons License.

AtmosphericChemistry

and PhysicsDiscussions

Multiwavelength and polarization lidar

measurements of Asian dust layers over

Tsukuba, Japan: a case study

T. Sakai, T. Nagai, T. Kobayashi, A. Yamazaki, A. Uchiyama, and Y. Mano

Meteorological Research Institute, Tsukuba, Japan

Received: 23 May 2007 – Accepted: 6 July 2007 – Published: 13 July 2007

Correspondence to: T. Sakai (tetsu@mri-jma.go.jp)

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Abstract

Elastic and polarization lidar was used to measure the vertical profiles of aerosol

backscattering coefficients at wavelengths of 355, 532, 735, and 1064 nm, and the

depolarization ratio at 532 nm in order to study the aerosol properties in the free tro-

posphere over Tsukuba, Japan, in 2006. An elevated dust layer was observed at5

altitudes between 3 and 8.5 km on 1 April during the Asian dust period. The wave-

length exponents of the aerosol backscattering coefficient (k) were –0.1 to 0.5, and

the depolarization ratio (δp) was 25% for the dust layer, suggesting the predominance

of supermicrometer-sized (coarse mode) nonspherical particles. An aerosol layer ob-

served at altitudes between 1.5 and 5 km on 19 October during the less-dust period10

exhibited the values of k=1.0 to 1.6 and δp=1 to 13%, suggesting the predominance

of submicrometer-sized (fine mode) particles. In those layers, the values of k and δp

varied with height; they were also negatively correlated, suggesting that the proportion

of the coarse nonspherical particles to total particles varied. The particle size distri-

butions estimated from the observed values and the theoretical computation revealed15

number mode radii of 0.3µm for the coarse mode and 0.1 µm for the fine mode, as-

suming bimodal distribution. These results were consistent with those obtained from

the sky-radiometer measurements, although they revealed another mode in the larger

radius. The column volume concentration derived from the lidar was 48% lower than

that derived from the sky-radiometer on 1 April and 16% lower on 19 October. The20

optical thickness derived from the lidar was 12% lower than that obtained from the sky-

radiometer on 1 April and 29% higher on 19 October. Further case study is necessary

to validate the method for estimating aerosol properties based on the lidar measure-

ment.

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1 Introduction

Mineral dust particles that originate from the arid and semi-arid lands of the Asian

Continent (Asian dust) are often transported and spread over East Asia and the North

Pacific, chiefly during the spring season (Iwasaka et al., 1988; Duce, 1995). The num-

ber of studies and programs focusing on the Asian dust has grown over the past few5

decades as the importance of regional climate and global biogeochemical cycles has

become increasingly apparent (Huebert et al., 2003; Arimoto et al., 2006; Mikami et

al., 2006). The dust can affect the Earth’s radiation balance by scattering and absorb-

ing solar and terrestrial radiation (Aoki et al., 2005; Shi et al., 2005), and it can affect

cloud properties by acting as cloud condensation nuclei and ice nuclei (e.g. Isono et10

al., 1959; Yamagata et al., 2004).

The impact of dust on the climate critically depends on particle properties such as

number concentration and size distribution, shape, chemical composition, and verti-

cal distribution (e.g. Liao and Seinfeld, 1998; Quijano et al., 2000). However, these

properties have not been adequately researched, particularly in the free troposphere,15

because of difficulties in measurement. Lidar is a useful tool for measuring the vertical

profiles of the aerosol optical properties. Multiwavelength and Raman lidar measure-

ments provide the aerosol optical properties that can be used for estimating particle

size distribution and the refractive index (e.g. Muller, 1999, 2000; Veselovskii et al.,

2005). The polarization lidar measurement provides the particle shape and phase20

(Sassen, 2000). However, few studies have used multiwavelength and polarization

data for estimating the aerosol properties.

This paper provides a case study of the multiwavelength and polarization lidar mea-

surement of the aerosol optical properties in the free troposphere over Tsukuba, Japan.

We studied the aerosol optical properties by focusing on the relation between the25

wavelength dependence of the backscattering coefficients and the depolarization ra-

tio. Based on the results of the measurement and the theoretical computation of the

aerosol optical properties, we estimated the fraction of fine and coarse particles in the

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backscattering coefficient and the size distribution. The estimated size distributions

were compared with those obtained from the sky-radiometer measurement.

2 Measurements

Multiple wavelength and polarization lidar measurements were carried out over

Tsukuba (36.0N, 140.1

E), which is located 60 km northeast of Tokyo. The charac-5

teristics of the lidar are presented in Table 1. The multiwavelength lidar transmits laser

pulses at wavelengths of 355 nm, 532 nm, 735 nm, and 1064 nm by use of three laser

sources: 1) Nd:YAG laser that transmits laser pulses with a repetition rate of 20 Hz

at 355 nm with a pulse energy of 80 mJ, and 532 nm with a pulse energy of 40 mJ;

2) Nd:YAG laser that transmits pulses at 1064 nm with 550 mJ/pulse at 20 Hz; and 3)10

Nd:YAG pumped-dye laser that transmits pulses at 735 nm with a 16 mJ/pulse at 10 Hz.

The light backscattered from atmospheric molecules and particles at wavelengths of

355 nm, 532 nm, and 1064 nm is collected by using a telescope with a diameter of

50 cm and a 3.0 mrad field of view (FOV). The light backscattered at a wavelength

of 735 nm is collected by using a telescope with a diameter of 35 cm and a FOV of15

2.2 mrad. The polarization lidar transmits laser pulses at 532 nm with 300 mJ/pulse and

10 Hz. The two orthogonal components of the linearly polarized elastic backscattering

at 532 nm are collected with telescopes with a diameter of 20 cm (FOV of 3.0 mrad)

and 40 cm (FOV of 2.0 mrad). The geometrical configurations of the lidar are in biaxial

except for the 20-cm telescope of the polarization lidar, which is coaxial. The lowest20

altitude of the measurement where the laser beam fully overlaps with receiver’s FOV

is 1.45 km for the multiwavelength lidar and 0.1 km for the polarization lidar. The col-

lected light is detected with photomultiplier tubes (PMTs) that are operated in photon

counting (PC) mode and analog-to-digital conversion (A/D) using transient recorders

(Licel GbR) with resolutions of 7.5 m in the vertical direction, and 1.5 or 3 min in time.25

We use PC data above an altitude of 2 km and A/D data below that altitude. The A/D

data are connected to PC data, multiplying a constant that is obtained by dividing the

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photon count by analog voltage at the height point of the connection.

The quantities obtainable with the multiwavelength lidar are the backscattering ratio

(R) and the particle backscattering coefficients (βp) at 355 nm, 532 nm, 735 nm, and

1064 nm. The value of R is proportional to the aerosol mixing ratio, and that of βp is

proportional to the concentration, assuming that the aerosol size distribution and the5

backscattering efficiency remain constant. To calculate these values, we used the it-

erative method (Fernald et al., 1972; Ismail et al., 1998). In the calculation, we used

the height-dependent particle extinction-to-backscatter ratios (lidar ratios, Sp) that were

estimated from the particle depolarization ratios. The estimation method is described

in Sect. 4. The backscatter signals were calibrated at altitudes of 10 to 15 km, assum-10

ing that the R was 1.01 at a wavelength of 355 nm, 1.03 at a wavelength of 532 nm,

1.09 at a wavelength of 735 nm, and 1.27 at a wavelength of 1064 nm, based on the

observations at midlatitude (Russell et al., 1979, 1982) and the wavelength depen-

dence of the backscattering coefficient for the continental aerosol model proposed by

Ackermann (1998). The molecular backscattering and extinction coefficients were cal-15

culated from the atmospheric temperature and pressure data that were obtained with

the radiosondes launched 250 m northeast of the lidar at 20:30 Japan standard time

(JST). The vertical resolution of the analyzed data was reduced to 150 m to improve

the signal-to-noise ratio. The uncertainty in the lidar-derived quantities was estimated

using Poisson statistics for the observed photon counts.20

We calculated the wavelength exponents (k) of the aerosol backscattering coefficient

between the four wavelengths (355 to 532 nm, 532 to 735 nm, and 532 to 1064 nm),

assuming the relation βp(λ)∝λ−k

. This value was negatively correlated with the mean

particle size; it was higher for the smaller particles and lower for the larger particles (e.g.

k∼1.5 for the submicrometer-sized particles and k∼0 for the supermicrometer-sized25

particles). We noted that the measured values of βp at 1064 nm had large uncertainty

in this study because of the low signal intensity at 1064 nm at the calibration height.

The measurement uncertainties in βp were on average 25% at 355 nm, 50% at 532 nm,

6% at 735 nm, and over 50% at 1064 nm for the studied altitude ranges.

10183

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The quantities obtainable with the polarization lidar are βp and the particle linear

depolarization ratio (δp) at 532 nm, defined by the ratio of the perpendicular to the

total components in βp with respect to the polarization plane of the emitted laser

light. This value is a measure of the particles’ nonsphericity if they are comparable

to or larger than the measurement wavelength (e.g. Mishchenko and Sassen, 1998).5

For example, mineral dust usually has high δp values (>10%) because it is mostly

supermicrometer-sized and nonspherical (Okada et al., 2001). In contrast, spherical

particles (e.g. droplets) and submicrometer-sized particles have low δp values (<10%).

3 Results

3.1 Case on 1 April 2006: Asian dust layer10

Figure 1a presents the vertical distributions of R, k, and δp that were obtained from

00:01 to 05:03 JST on 1 April 2006. High values of R exceeding 1.5 at 532 nm were

obtained at altitudes between 3.0 and 8.5 km, with a peak value of 2.45 at an altitude

of 3.8 km. The optical thickness was estimated to be 0.27 at 532 nm for this altitude

range. The values of k were low, ranging from –0.1 to 0.5 (thin lines in the right panel of15

Fig. 1a), suggesting that supermicrometer-sized (coarse) particles were predominant.

The values of δp were as high as 25% (thick solid line in the right panel of Fig. 1a),

indicating that coarse nonspherical particles were predominant. It should be noted that

the values of δp and k varied with height, and they were negatively correlated (see

also Fig. 3). These results suggested that the fraction of coarse nonspherical parti-20

cles that have higher δp and lower k values than those of the fine particles varied

with height. This is discussed further in Sect. 4. The coarse nonspherical particles

were probably mineral dust particles originating from the arid or semi-arid lands of the

Asian continent: back trajectory analysis revealed that the air parcels had been trans-

ported over the arid and semi-arid lands of the Asian continent and over the northern25

part of the Taklimakan Desert three days earlier (Fig. 2a). Details of the method for

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computing the trajectory are given by Sakai et al. (2000). The reasons why we calcu-

lated many trajectories located around the lidar site (25 points in steps of 0.5 degrees

for longitude and latitude) are to consider the possibility of the mixing of different air

masses that had passed over the source areas as well as to reduce the uncertainty of

the trajectory that can be arisen from the coarse resolution of the meteorological data5

(1.25 degrees for longitude and latitude) used in the computation. In addition to the

trajectory analysis, the aerosol transport model of Navy Aerosol Analysis and Predic-

tion System (NAAPS) also predicted the presence of dust with a mass concentration

of 15 to 50µgm−3

between 2 and 7 km in height and sulphates with 1–2µgm−3

be-

tween 2 and 3 km over the lidar site (http://www.nrlmry.navy.mil/aerosol web/globaer/10

ops 01/tsukub/200604/2006032700 2006040100 tsukub.gif). For comparison of the

optical properties of the Asian dust, Murayama et al. (2004) observed k of 0.3 to 1.2

at 355 to 532 nm and δp of 18% at altitudes between 3 and 5 km over Tokyo during

the Asian dust period. Sugimoto and Lee (2006) observed k∼0.5 at 532 to 1064 nm

and δp∼10% at an altitude of 2 km for the Asian dust layer over Korea. Our measured15

values were a little lower for k (–0.1 to 0.5) and higher for δp (25%) than their reported

values. This difference was possibly due to the higher fraction of coarse particles in

the dust layer that we measured. Ansmann et al. (2002) observed k ranging from –0.5

to 0 at 355 to 532 nm and δp ranging from 10% to 20% at altitudes between 1 and

5 km for the Saharan dust layers over Europe. These values were a little lower than20

our results, possibly due to the differences in the fraction of coarse particles and the

optical properties between the Saharan dust and Asian dust over the remote sites.

3.2 Case on 19 October: fine particle layer

Figure 1b plots the vertical profiles obtained during the less-dust period for 02:01 to

06:45 JST on 19 October 2006. The profile of R indicated peak values of 1.3 at an25

altitude of 4.3 km, and 1.9 at 2 km at 532 nm. The optical thickness was estimated to

be 0.09 at 532 nm between 1.45 and 4.7 km. The values of k ranged from 1.0 to 1.6 in

those regions, suggesting that submicrometer-sized (fine) particles were predominant.

10185

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The values of δp were 1 to 13%, indicating that spherical and/or small (compared with

the laser wavelength of 532 nm) particles were predominant. It should again be noted

that δp and k were negatively correlated (Figs. 1 and 3). Clustered backward trajectory

analysis revealed that the majority of the air parcels for that altitude region had passed

over the industrial regions of the coastal area in China (30 to 35N, 105 to 120

E), and5

two parcels had passed over the Taklimakan Desert regions (Fig. 2b). The NAAPS

model predicted the presence of a relatively small amount of dust (15 to 25µgm−3

)

and sulphates (1 to 2µgm−3

) below 4 km over the lidar site. These results suggested

that the Asian dust and sulphates were both present in the aerosol layers measured

with the lidar.10

4 Estimation of particle size distribution

We estimated the particle size distributions of the aerosol layers measured with the lidar

by comparison with an aerosol model based on the results of the airborne measure-

ments in the free troposphere near the lidar site (Takamura et al., 1990; Matsuki et al.,

2003; Sakai et al., 2003; Murayama et al., 2004). The model assumes that the optically15

effective aerosols were composed primarily of two components: submicrometer-sized

ammonium bisulphates in the fine mode and supermicrometer-sized mineral dust in

the coarse mode. In the calculation of the optical properties of these particles, the sul-

phate particles were assumed to be spherical droplets with a refractive index of 1.46+0i

(Tang and Munkelwitz, 1994) and a lognormal size distribution with a geometric stan-20

dard deviation (σg) of 1.66 (Sakai et al., 2003). The dust particles were assumed to

be triaxial spheroids with a length-to-width ratio of 1.4 and a height-to-width ratio rang-

ing from 0.2 to 1.0, based on the morphological study of the Asian dust by Okada

et al. (2001). The refractive index of 1.5+0.001i (Aoki et al., 2005; Kalashnikova and

Sokolik, 2004; Arimoto et al., 2006) and a lognormal distribution with σg=2.0 (Sokolik25

and Toon, 1999) were assumed for this particle mode. To compute the aerosol optical

properties, we used the Mie code (Bohren and Huffman, 1983) for the fine mode and

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the combined field integration (CFIE) method (Mano, 2000) for the coarse mode. The

geometric number mean radii (rNg ) of the two modes were determined in an effort to

minimize the difference between the computed values of k and δpand those obtained

with the lidar by varying rNg as described below.

To interpret the observed aerosol optical properties, we expressed the aerosol5

backscattering coefficient observed with the lidar (βobs) by

βobs=βf+βc, (1)

where the subscript f refers to the fine mode particles, and c refers to the coarse mode

particles. If we define the fraction of β of the coarse mode particles in total (fine +

coarse) particles by10

fc=βc

βf+βc

=βc

βobs

, (2)

then the wavelength exponent of the backscattering coefficient observed with the lidar

(kobs) is expressed by

(

λ2

λ1

)

−kobs

=(1 − fc)

(

λ2

λ1

)

−kf

+fc

(

λ2

λ1

)

−kc

, (3)

where λ1=532 nm and λ2=355, 735, or 1064 nm. The particle depolarization ratio ob-15

served with the lidar (δobs) is expressed by

δobs=(1−fc)δf+fcδc. (4)

To determine kf , kc, and δc (δf is zero because the fine mode particles were assumed

to be spherical droplets), we compared the lidar-derived k and δp with those computed

for the aerosol optical model. Figure 3 presents the scatter diagram of k as a function20

of δp obtained with the lidar and those computed by the model. We determined kc, δc,

and kf in order to minimize the difference between the observed and modelled values.

The lidar-derived values (solid diamonds in Fig. 3) fit to a line of the model for which fc10187

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varied between 0 and 1 (thick solid line with open squares and numbers in Fig. 3). The

rNg varied from 0.02 to 0.4µm in steps of 0.02µm (thin line with open circles) for the

fine mode and from 0.2 to 2.0µm in steps of 0.1µm for the coarse mode (thin line with

open triangles).

We found that the lidar-derived values most closely fit the computed values when5

rNg =0.1µm for the fine mode and r

Ng =0.3µm for the coarse mode. These radii were

consistent for the fine mode and a little smaller than the previously reported values

obtained from the airborne optical particle counter measurements (0.05 to 0.1µm for

the fine mode and 0.4 to 0.5µm or 1µm for the coarse mode) (Takamura et al., 1990;

Sakai et al, 2003; Matsuki et al., 2003), and consistent with those derived from the10

sky-radiometer measurements (Fig. 5). The optical properties computed for these two

modes are given in Table 2. For comparison of the computed aerosol optical properties

with those obtained from field experiments, Takamura et al. (1994) obtained Sp of 61 sr

at 532 nm by use of the elastic lidar and sunphotometer data over Tsukuba in Novem-

ber 1990, when the Asian dust was rare. This value was close to our computed value15

for the fine mode. Murayama et al. (2004) obtained Sp∼ 49 sr at 355 nm, Sp∼43 sr at

532 nm, and δp∼20% for the Asian dust layers over Tokyo by use of the Raman and

polarization lidar. Sakai et al. (2003) reported Sp=47±18 sr at 532 nm and δp=20±7%

for the Asian dust layers over Tsukuba by the same technique. These values were

close to or a little lower than our computed values for the coarse mode. It is neces-20

sary to determine the Sp and δp of the Asian dust in a consistent manner such like

laboratory experiment using a chamber.

For the estimation of fc averaged for the aerosol layers, Fig. 4 compares k at the

three wavelength pairs (355 to 532 nm, 532 to 735 nm, and 532 to 1064 nm) andδp

obtained with the lidar (solid symbols) and those calculated from the model (open sym-25

bols) for the aerosol layers observed for the two periods. The averaged fc values were

0.84 for the aerosol layer on 1 April (height range between 1.5 and 9.4 km) and 0.17

on 19 October (height range between 1.5 and 4.7 km).

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In order to determine Sp, we expressed Sp in a similar manner to δp in Eq. (4) by

Sp=(1−fc)Sf+fcSc. (5)

By substituting Sf and Sc given in Table 2 and fc obtained from the lidar-derived δp

profile (by Eq. 4) into Eq. (5), we obtained Sp as a function of height. The obtained

values were used to compute the vertical profiles of βp at the four wavelengths. We5

used δp Eq. (4) instead of k Eq. (5) to estimate fc because the measurement uncer-

tainty in δp is lower than that in k. It was necessary to iterate the computation to derive

these values (βp, δp, and Sp) because they are mutually dependent. We found that

fc ranged from 0.81 to 1 on 1 April and from 0.07 to 0.36 on 19 October (Fig. 3). The

corresponding Sp values were 55–56, 62, 67–69, and 71–78 sr on 1 April and 50–52,10

61, 59–62, and 45–55 sr on 19 October at 355, 532, 735, and 1064 nm. It should be

noted that fc decreased with height above an altitude of 3 km on 1 April (which could be

expected from the decrease in δp with height in Fig. 1a), suggesting that the fraction of

the coarse-mode particles decreased with height. This result was possibly due to the

faster gravitational settling of the coarse particles than that of the fine particles.15

Based on these results, we estimated the column particle concentration and size

distribution. The column total particle number concentrations (N) were estimated from

βp and fc by

N=Nc+Nf , (6)

where20

Nc=

∫ ztop

0

fc(z)βp(z)dz

/

dσc

dΩ, (7)

for the coarse mode and

Nf=

∫ ztop

0

[1 − fc(z)]βp(z)dz

/

dσf

dΩ(8)

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for the fine mode, wheredσXdΩ

is the mean volume backscattering cross section of x-

mode particles calculated from the model (Table 2). We used βp at 532 nm because

the minimum level of the measurement was the lowest (0.1 km in height) and the

measurement uncertainty in the signal was the smallest among the four wavelengths.

We set ztop 15 km and used the values at 0.1 km for the height integration between5

the ground and 0.1 km. The column number concentrations were calculated to be

1.1×108

cm−2

(Nc=0.2×108

cm−2

and Nf=0.9×108

cm−2

) on 1 April and 7.3×108

cm−2

(Nc=2.4×106

cm−2

and Nf=7.3×108

cm−2

) on 19 October.

5 Comparison with sky-radiometer measurement

Figure 5 plots the columnar volume size distributions for the two periods. It indi-10

cates the predominance of the coarse mode on 1 April and the fine mode on 19

October. For comparison of the size distribution, Fig. 5 also presents the size dis-

tributions derived from the sky-radiometer measurement 180 m east of the lidar at

06:40 JST on 1 April and 07:00 JST on 19 October 2006. The method for retrieving the

size distribution from the sky-radiometer measurement is described by Uchiyama et15

al. (2005a, b) and Kobayashi et al. (2006). The size distributions derived from the sky-

radiometer indicated a tri-modal distribution with volume mode radii (rVg ) of 0.25µm,

1.16–1.69µm, and 3.62µm. The first and second mode radii were close to those esti-

mated from the lidar data for the fine mode with rVg=0.2µm (computed using the rela-

tion ln rVg=lnr

Ng +ln

2σg) and coarse mode with r

Vg=1.3µm. The third mode radius could20

not be captured by the lidar data because we assumed a bimodal distribution. The total

volume concentrations (V ) were 0.19µm3µm

−2(Vf=0.01 and Vc=0.18µm

3µm

−2) on

1 April and 0.12µm3µm

−2(Vf=0.1 and Vc=0.02µm

3µm

−2), whereas those obtained

from the sky-radiometer were 0.37µm3µm

−2(Vf=0.03 and Vc=0.34µm

3µm

−2) on 1

April and 0.14µm3µm

−2(Vf =0.06 and Vc=0.08µm

3µm

−2) on 19 October. The lidar-25

derived V were lower than those derived by the sky-radiometer by 48% on 1 April and

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16% on 19 October. The reason for the difference between the lidar and sky-radiometer

data is currently unresolved but is probably related to the uncertainty in the assump-

tions made for calculating the aerosol properties from the measurement data and the

spatial and temporal variability of the aerosol properties between the two measure-

ments. The optical thicknesses (τ) at 532 nm derived from the lidar data were 0.44 on5

1 April and 0.67 on 19 October, whereas those obtained from the sky-radiometer data

were 0.50 on 1 April and 0.52 on 19 October, calculated by interpolating τ at 500 and

650 nm. The lidar-derived τ were 12% lower than that obtained with the sky-radiometer

on 1 April and 29% higher on 19 October.

More case studies are necessary to validate the method for estimating the particle10

size distribution from the lidar data because we used a simple model for calculating the

aerosol optical properties. We assumed the two aerosol components of which particle

shape, refractive index, and the size distribution shape (σg of the lognormal distribution)

were constant over the height; only their proportion (fc) varied with height. Moreover,

the measurement data used in this study were taken for only the two periods when15

the transportation pathways of the air parcels were similar (westerly winds prevailed

over the lidar site), so that potential source regions and the predominant aerosol con-

stituents might also be similar. If the predominating aerosol constituents were different

from this case study, the parameters (kc, δc, and kf ) of the aerosol model should be

modified. In addition, the lidar-derived values must be compared with those obtained20

with the in-situ aerosol instruments (e.g. particle counters) to validate the results.

6 Conclusions

The vertical profiles of aerosol backscattering coefficients and depolarization ratio were

measured by use of multiwavelength and polarization lidar over Tsukuba, Japan, in

2006. The Asian dust layer between altitudes of 3 and 8.5 km on 1 April revealed25

k=–0.1 to 0.5 and δp∼25%. The aerosol layer between 1.5 and 5 km on 19 October

revealed k= 1.0 to 1.6 and δp=1 to 13%. The values of k and δp varied with height, and

10191

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they were negatively correlated in those layers, suggesting that the proportion of the

coarse nonspherical dust particles to the total particles varied with height. The fraction

of the coarse particles in total backscattering was estimated to vary from 0.81 to 1 with

an average of 0.84 on 1 April, and from 0.07 to 0.36 with an average of 0.17 on 19

October. The mode radii of these particles were estimated to be 0.3µm for the coarse5

mode and 0.1µm for the fine mode based on k and δp values obtained with the lidar

and the aerosol model. The column volume concentrations derived from the lidar were

0.19µm3µm

−2on 1 April and 0.12µm

3µm

−2on 19 October. These concentrations

were 48% lower than those derived from the sky-radiometer on 1 April and 16% lower

on 19 October. The optical thicknesses derived from the lidar were 0.44 on 1 April10

and 0.67 on 19 October, which were lower than that derived from the sky-radiometer

by 12% on 1 April and higher by 29% on 19 October. The reason for the differences

is not resolved but probably the incorrectness of assumptions of the aerosol model

used for calculating the aerosol properties from the measured data and temporal and

spatial variability of the aerosol properties between the measurements. Further case15

studies and comparisons with in-situ measurements are needed to validate the method

for estimating the aerosol properties from the lidar measurement.

References

Ackermann, J.: The extinction-to-backscatter ratio of tropospheric aerosol: a numerical study,

J. Atmos. Ocean. Tech., 15, 1043–1050, 1998.20

Ansmann A., Wagner, F., Muller, D., Althausen, D., Herber, A., von Hoyningen-Huene, W.,

and Wandinger, U.: European pollution outbreaks during ACE 2: Optical particle properties

inferred from multiwavelength lidar and star-Sun photometry, J. Geophys. Res., 107(D15),

4259, doi:10.1029/2001JD001109, 2002.

Aoki, T., Tanaka, T. Y., Uchiyama, A., Chiba, M., Mikami, M., Yabuki, S., and Key, J. R.: Sensi-25

tivity experiments of direct radiative forcing caused by mineral dust simulated with a chemical

transport model, J. Meteorol. Soc. Jpn., 83A, 315–331, 2005.

Arimoto, R., Kim, Y. J., Kim, Y. P., Quinn, P. K., Bates, T. S., Anderson, T. L., Gong, S., Uno,

10192

ACPD

7, 10179–10203, 2007

Lidar measurements

of Asian dust

T. Sakai et al.

Title Page

Abstract Introduction

Conclusions References

Tables Figures

Back Close

Full Screen / Esc

Printer-friendly Version

Interactive Discussion

EGU

I., Chin, M., Huebert, B. J., Clarke, A. D., Shinozuka, Y., Weber, R. J., Anderson, J. R.,

Guazzotti, S. A., Sullivan, R. C., Sodeman, D. A., Prather, K. A., and Sokolik, I. N.: Charac-

terization of Asian Dust during ACE-Asia, Global and Planet. Change, 52, 23–56, 2006.

Bohren, C.F. and D. R. Huffman: Absorption and Scattering of Light by Small Particles Wiley,

New York, 1983.5

Dubovik, O. and King, M. D.: A flexible inversion algorithm for retrieval of aerosol properties

from sun and sky radiance measurements, J. Geophys. Res., 105, 20 673–20 696, 2000.

Duce, R. A.: Sources, distributions, and fluxes of mineral aerosols and their relationship to

climate, in Aerosol Forcing of Climate, edited by: Charlson, R. J. and Heitzenberg, J., John

Wiley, New York, pp.43–72, 1995.10

Fernald, F. G., Herman, B. M., and Reagan, J. A.: Determination of aerosol height distributions

by lidar, J. Appl. Meteorol., 11, 482–489, 1972.

Huebert, B. J., Bates, T., Russell, P. B., Shi, G. Y., Kim, Y. J., Kawamura, K., Carmichael,

G., and Nakajima, T.: An overview of ACE-Asia: Strategies for quantifying the relation-

ships between Asian aerosols and their climatic impacts, J. Geophys. Res., 108(D23), 8633,15

10.1029/2003JD003550, 2003.

Ismail, S., Browell, E. V., Ferrare, R. A., Kooi, S. A., Clayton, M. B., Brackett, V. G., and Russell,

P. B.: LASE measurements of aerosol and water vapor profiles during TARFOX, J. Geophys.

Res., 105, 9903–9916, 2000.

Isono, K., Komabayashi, M., and Ono, A.: The nature and the origin of ice nuclei in the atmo-20

sphere, J. Meteorol. Soc. Jpn., 37, 211–233, 1959.

Iwasaka, Y., Yamato, M., Imasu, R., and Ono, A.: Transport of Asian dust (KOSA) particles;

importance of weak KOSA events on the geochemical cycle of soil particles, Tellus, 40B,

494–503, 1988.

Kalashnikova, O. V. and Sokolik, I. N.: Modelling the radiative properties of nonspherical soil-25

derived mineral aerosols, J. Quant. Spectrosc. Ra., 87, 137–166, 2004.

Kobayashi, E., Uchiyama, A., Yamazaki, A., and Matsuse, K.: Application of the statistical

optimization method to the inversion algorithm for analyzing aerosol optical properties from

sun and sly radiance measurement, J. Meteorol. Soc. Jpn., 84, 1047–1062, 2006.

Liao, H. and Seinfeld, J. H.: Effect of clouds on direct aerosol radiative forcing on climate, J.30

Geophys. Res., 103, 3781–3788, 1998.

Muller, D., Wandinger, U., and Ansmann, A.: Microphysical particle parameters from extinction

and backscatter lidar data by inversion with regularization: Theory, Appl. Optic, 38, 2346–

10193

ACPD

7, 10179–10203, 2007

Lidar measurements

of Asian dust

T. Sakai et al.

Title Page

Abstract Introduction

Conclusions References

Tables Figures

Back Close

Full Screen / Esc

Printer-friendly Version

Interactive Discussion

EGU

2357, 1999.

Muller, D., Wagner, F., Wandinger, U., Ansmann, A., Wendisch, M., Althausen, D., and von

Hoyningen-Huene, W.: Microphysical particle parameters from extinction and backscatter

lidar data by inversion with regularization: Experiment, Appl. Optic, 39, 1879–1892, 2000.

Mano, Y.: Exact solution of electromagnetic scattering by a three-dimensional hexagonal ice5

column obtained with the boundary-element method, Appl. Optic, 39, 5541–5546, 2000.

Matsuki, A., Iwasaka, Y., Osada, K., Matsunaga, K., Kido, M., Inomata, Y., Trochkine, D.,

Nishita, C., Nezuka, T., Sakai, T., Zhang, D., Kwon, S.-A.: Seasonal dependence of the

long-range transport and vertical distribution of free tropospheric aerosols over east Asia:

On the basis of aircraft and lidar measurements and isentropic trajectory analysis, J. Geo-10

phys. Res., 108(D23), 8663, doi:10.1029/2002JD003266, 2003.

Mikami, M., Shi, G.-Y., Uno, I., Yabuki, S., Iwasaka, Y., Yasui, M., Aoki, T., Tanaka, T. Y.,

Kurosaki, Y., Masuda, K., Uchiyama, A., Matsuki, A., Sakai, T., Takemi, T., Nakawo, M.,

Seino, N., Ishizuka, M., Satake, S., Fujita, K., Hara, Y., Kai, K., Kanayama, S., Hayashi,

M., Du, M., Kanai, Y., Yamada, Y., Zhang, X.-Y., Shen, Z. , Zhou, H., Abe, O., Nagai,15

T., Tsutsumi, Y., Chiba, M., and Suzuki, J.: Aeolian Dust Experiment on Climate Impact:

An Overview of Japan-China Joint Project ADEC, Global Planet. Change, 52, 142–172,

doi:10.1016/j.gloplacha.2006.03.001, 2006.

Murayama, T., Muller, D., Wada, K., Shimizu, A., Sekiguchi, M., and Tsukamoto, T.: Charac-

terization of Asian dust and Siberian smoke with multi-wavelength Raman lidar over Tokyo,20

Japan in spring 2003, Geophys. Res. Lett., 31, L23103, doi:10.1029/2004GL021105, 2004.

Okada, K., Heintzenberg, J., Kai, K., and Qin, Y.: Shape of atmospheric mineral particles

collected in three Chinese arid-regions, Geophys. Res. Lett., 28(16), 3123–3126, 2001.

Quijano, A. L., Sokolik, I. N., and Toon, O. B.: Radiative heating rates and direct radiative

forcing by mineral dust in cloudy atmospheric conditions, J. Geophys. Res., 105, 12 207–25

12 220, doi:10.1029/2000JD900047, 2000.

Russell, P. B., Swissler, T. J., and McCormick, M. P.: Methodology for error analysis and simu-

lation of lidar aerosol measurements, Appl. Optic, 18, 3783–3797, 1979.

Russell, P. B., Morley, B. M., Livingston, J. M., Grams, G. W., and Patterson, E. M.: Orbiting lidar

simulations. 1: Aerosol and cloud measurements by an independent-wavelength technique,30

Appl. Optic, 21, 1541–1553, 1982.

Sakai, T., Shibata, T., Kwon, S. A., Kim, Y. S., Tamura, K., and Iwasaka, Y.: Free tropospheric

aerosol backscatter, depolarization ratio and relative humidity measured with the Raman

10194

ACPD

7, 10179–10203, 2007

Lidar measurements

of Asian dust

T. Sakai et al.

Title Page

Abstract Introduction

Conclusions References

Tables Figures

Back Close

Full Screen / Esc

Printer-friendly Version

Interactive Discussion

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lidar at Nagoya in 1994-1997: contributions of aerosols from the Asian continent and the

Pacific Ocean, Atmos. Environ., 34, 431–442, 2000.

Sakai, T., Nagai, T., Nakazato, M., Mano, Y., and Matsumura, T.: Ice clouds and Asian dust

studied with lidar measurements of particle extinction-to-backscatter ratio, particle depolar-

ization, and water vapor mixing ration over Tsukuba, Appl. Optic, 42, 7103–7116, 2003.5

Sakai, T., Shibata, T., Hara, K., Kido, M., Osada, K., Hayashi, M., Matsunaga, K., and Iwasaka,

Y.: Raman lidar and aircraft measurements of tropospheric aerosol particles during the Asian

dust event over central Japan: Case study on 23 April 1996, J. Geophys. Res., 108(D12),

4349, 10.1029/2002JD003150, 2003.

Sassen, K.: Lidar backscatter depolarization technique for cloud and aerosol research, in Light10

Scattering by Nonspherical Particles: Theory, Measurements, and Applications, edited by:

Mishchenko, M. L., Hovenier, J. W., and Travis, L. D., pp.393–416, Academic Press, San

Diego, 2000.

Shi, G., Wang, H., Wang, B., Li, W., Gong, S., Zhao, T., and Aoki, T.: Sensitivity experiments

on the effects of optical properties of dust aerosols on their radiative forcing under clear sky15

condition, J. Meteorol. Soc. Jpn., 83A, 333–346, 2005.

Sokolik, I. N. and Toon, O. B.: Incorporation of mineralogical composition into models of the

radiative properties of mineral aerosol from UV to IR wavelengths, J. Geophys. Res., 104,

9423–9444, 1999.

Sugimoto, N. and Lee, C. H.: Characteristics of dust aerosols inferred from lidar depolarization20

measurements at two wavelengths, Appl. Optic, 45, 7468–7474, 2006.

Takamura, T., Sasano, Y., and Hayasaka, T.: Troposheric aerosol optical properties derived

from lidar, sun photometer, and optical particle counter measurements, Appl. Optic, 33,

7132–7140, 1994.

Takamura, T. and Sasano, Y.: Aerosol optical properties inferred from simultaneous lidar,25

aerosol-counter, and sunphotometer measurements, J. Meteorol. Soc. Jpn., 68, 729–739,

1990.

Tang, I. N. and Munkelwitz, H. R.: Water activities, densities, and refractive indices of aque-

ous sulfates and sodium nitrate droplets of atmospheric importance, J. Geophys. Res., 99,

18 801–18 808, 1994.30

Uchiyama, A., Yamazaki, A., Togawa, H., and Asano, J.: Characteristics of Asian dust observed

by sky-radiometer in the Intense Observation Period 1 (IOP1), J. Meteorol. Soc. Jpn., 83A,

291–305, 2005a.

10195

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Uchiyama, A., Yamazaki, A., Togawa, H., Asano, J., and Shi, G.: Single scattering albedo of

aeolian dust as inferred from sky-radiometer and in situ ground based measurement, SOLA,

1, 209–212, 2005b.

Veselovskii, I., Kolgotin, A., Muller, D., and Whiteman, D. N.: Information content of multiwave-

length lidar data with respect to microphysical particle properties derived from eigenvalue5

analysis, Appl. Optic, 44, 5292–5303, 2005.

Yamagata, S., Kuroda, T., Zaima, T., Murao, N., Ohta, S., Fujiyoshi, Y., Harimaya, T., Yamada,

T., Izumi, K., Fukuyama, T., and Utiyama, M.: Mineral particles in cloud droplets produced in

an artificial cloud experimental system (ACES), Aerosol Sci. Tech., 38, 293–299, 2004.

10

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Table 1. Specification of lidar used in this study.

Lidar type Multiwavelength lidar Polarization lidar

Transmitter

Wavelength (nm) 355 532 1064 735 532

Laser type

(Continuum, Inc.)

Nd:YAG (PL8020) Nd:YAG

(YG581C)

ND:YAG-pumped

Dye (TDL60)

Nd:YAG

(SL2)

Repetition rate (Hz) 20 20 10 10

Energy/pulse (mJ) 80 40 550 16 300

Beam divergence (mrad) 0.125 0.125 0.125 2.0 0.2

Receiver

Telescope type Nasmyth Schmidt-Cassegrain Schmidt-Cassegrain

Diameter (m) 0.5 0.35 0.2, 0.4

Field of view (mrad) 3.0 2.2 3.0, 2.0

Detection wavelength (nm) 355 532 1064 735 532

Detection species Elastic Elastic Elastic Elastic Elastic and Polarization

Filter bandwidth (nm) 0.50 0.57 0.46 3.00 0.50

Photomultiplier tubes

(Hamamatsu Photonics)

R1332 R1332 R3236-01 R1333 R3234-01

Detection mode* PC and A/D PC and A/D PC and A/D

Range resolution (m) 7.5 7.5 7.5

Temporal resolution (min) 1.5 3 3

∗

PC: Photon counting. A/D: analog-to-digital conversion.

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Table 2. Optical properties computed for the aerosol model.

Mode Fine Coarse

Species ammonium bisulphate mineral dust

Refractive index 1.46+0i 1.5+0.001i

Size distribution

geometric mean radius(µm)* 0.1 0.3

geometric standard deviation 1.66 2

Shape sphere triaxial ellipsoid**

Wavelength (nm) 355 532 735 1064 355 532 735 1064

k (532 nm-λ) 1.55 – 1.47 1.38 –0.15 – 0.22 0.38

δp (%) – 0 – – – 27 – –

Sp (sr) 50 61 58 42 56 62 69 78

dσ/dΩ (10−14

m2

sr−1

) 1.2 0.5 0.6 0.4 3.6 3.8 3.6 3.0

∗

Values were estimated from the lidar measurements (see Sect. 3).∗∗

Length-to-height ratio was 1.4, and height-to-width ratio ranged from 0.2 to 1.0, based on

microscopic measurement of Asian dust by Okada et al. (2001).

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(a)-0.5 0 0.5 1 1.5 2

Wavelength Exponent

Depolarization Ratio

355/532 nm 735/532 nm1064/532 nm Depolarization

0 10 20 30

(b)

-0.5 0 0.5 1 1.5 2

Wavelength Exponent

Depolarization Ratio (%)

355/532 nm 735/532 nm1064/532 nm Depolarization

0 10 20 30

Fig. 1. Vertical distribution of the particle optical properties that were obtained with the lidar for

the period 00:01–05:03 JST on 1 April 2006 (a) and 02:01–06:45 JST on 19 October 2006 (b)

over Tsukuba. The left panels show the backscattering ratios at wavelengths of 355, 532, 735,

and 1064 nm. The right panels show the wavelength exponent of the backscattering coefficients

and the particle depolarization ratio at 532 nm.

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(a)

30

60

5-day isentropic backward trajectorieson 1 April 2:00 JST

Latit

ude(

o N)

Lidar siteAltitude:4 km

60 90 120 150Longitude(oE)

3

6

9

Alti

tude

(km

)

(b)

30

60

5-day isentropic backward trajectorieson 19 October 4:00 JST

Latit

ude(

o N)

Lidar siteAltitude:4 km

60 90 120 150Longitude(oE)

3

6

9

Alti

tude

(km

)

Fig. 2. Clustered isentropic backward trajectories of the air parcels arriving over the lidar site

at an altitude of 4 km on 1 April (a) and 19 October (b) in 2006. Symbols are plotted at 24-h

intervals. The lowermost lines in the vertical cross section show the land elevations.

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(a)

0 0.20.4

0.60.8

1

-3

-2

-1

0

1

2

3

0 10 20 30

Particle Depolarization Ratio (%)

Bac

ksca

tter W

avel

en

gth

Exp

on

ent.

(35

5/5

32

nm

)

Coarse ModeFraction

2 µm

rgN(coarse):

0.3 µm

rgN(fine):

0.1 µm

0.02 µm

0.4 µm

0.2 µm

1 April19 October

(b)

00.2

0.40.6

0.81

-3

-2

-1

0

1

2

3

0 10 20 30

Particle Depolarization Ratio (%)

Ba

cksc

atte

r W

ave

len

gth

Exp

on

ent.

(532

/735

nm

)

Coarse ModeFraction

2 µm

rgN(coarse):

0.3 µm

rgN(fine):

0.1 µm

0.02 µm

0.4 µm

0.2 µm

1 April19 October

(c)

0 0.2 0.40.6 0.8 1

-3

-2

-1

0

1

2

3

0 10 20 30

Particle Depolarization Ratio (%)

Ba

cksc

atte

r W

ave

len

gth

Exp

one

nt.

(532

/106

4 n

m)

Coarse ModeFraction

2 µm

rgN(coarse):

0.3 µm

rgN(fine):

0.1 µm

0.02 µm

0.4 µm0.2 µm

1 April19 October

Fig. 3. Scatter diagrams of wavelength exponent of backscattering coefficients as a function

of depolarization ratio. The wavelength exponents were between 355 and 532 nm (a), 532 and

735 nm (b), and 532 and 1064 nm (c). Solid diamonds indicate the measured values. Open

symbols (circles for the fine mode and triangles for the coarse mode) denote the computed

values for which the mode radii varied from 0.02 to 0.4µm and 0.2 to 2.0µm. Numbers (0 to 1)

on a solid line with open squares represent the ratio of coarse to total particles; the mode radii

was 0.3µm for the coarse mode and 0.1µm for the fine mode.

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-1

0

1

2

Wavelength λ (nm)

Bac

ksca

tter

Wav

elen

gth

Exp

onen

t( λ

/532

nm

)

355 735 1064

19 October (Height Range: 1.5-4.7 km)

1 April (Height Range: 1.5-9.4 km)

Model (Dust Fraction: 0.17)

Model (Dust Fraction: 0.84)

0

10

20

30

Par

ticle

Dep

olar

izat

ion

Rat

io (

%)

532

Fig. 4. Comparison of wavelength exponent of backscattering coefficients between 355 and

1064 nm (left panel) and particle depolarization ratio (right panel) between the lidar-derived

values and the models. Solid symbols indicate the lidar-derived values averaged for heights of

1.5 to 9.4 km on 1 April (diamonds) and of 1.5 to 4.7 km on 19 October (circles). Open symbols

denote the values obtained using the model, assuming the dust fraction of 0.84 (diamonds) and

0.17 (circles) that fit the measurements. The error bar indicates the standard deviation in the

height ranges.

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(a)

1 April 2006

0

0.1

0.2

0.01 0.1 1 10

Particle Radius (µm)

Col

umn

dV/d

ln r

( µm

)

Lidar

Sky-radiometer

(b)

19 October 2006

0

0.1

0.2

0.01 0.1 1 10

Particle Radius (µm)C

olum

n dV

/dln

r ( µ

m)

Lidar Sky-radiometer

Fig. 5. Column particle volume size distributions estimated from the lidar measurements (solid

line with diamonds) and those derived from sky-radiometer measurement (dotted line with

squares) over Tsukuba on 1 April (a) and 19 October (b) in 2006. The error bars denote

the uncertainties estimated from the lidar signal.

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